The invention relates to novel copolymers prepared by the interaction of a melt mix of a high molecular polyarylate, or a low molecular weight polyarylate of, for example, bisphenol A-isophthalate-terephthalate polyarylate, or bisphenol A-isophthalate-terephthalate-carbonate polyarylate and a high molecular weight diprimary dialcohol polyester polymer, such as polyethylene arylate, and to the process for their manufacture.
In order to produce polyarylates of high molecular weights temperatures of 300.degree. C. or more are normally required. The problem is that at this range, thermal degradation and discoloration occurs. The process of the subject invention minimizes the polymerizing temperature and also produces novel copolymers which are transparent, tough, maintain dimensional stability, and are not discolored. They are completely soluble in chloroform and have a single glass transition temperature.
It has been proposed to prepare mixed polyesters having a softening temperature above 100.degree. C.: U.S. Pat. No. 3,299,172 granted Jan. 17, 1967 and U.S. Pat. No. 3,413,379 granted Nov. 26, 1968. In these prior patents a mixture of diphenyl isophthalate, diphenyl terephthalate, diphenyl carbonate and bisphenol A are disclosed in the Examples as being reacted until the mixture reaches a value of 2,000 to 4,000 poises. At this point there is added to this mixture a polyester of a diprimary dihydric alcohol and terephthalic or isophthalic acid.
In U.S. Pat. No. 3,299,172 it is stated, column 3, lines 16 and 17 that the products obtained are opaque and generally faintly yellowish colored masses. In Example 1, it is stated that the product was faintly yellowish in color, and had a slightly milky appearance (Col. 4, lines 8-9). It is also stated that in hot chloroform, a portion of the polyester product went into solution, while a swelled residue thereof remained undissolved (Col. 3, lines 10-12). Turbidity of the resulting product and its yellow coloration are also mentioned in other of the examples.
In U.S. Pat. No. 3,413,379 it is stated that: "Thus, the invention herein constitutes the use of certain low molecular weight polyesters, i.e., those having a viscosity number of between about 0.1 and 0.5 dl./g. as an additive to the reaction mixture of diaryl terephthalate and/or diaryl isophthalate with dihydric phenols at a specified point during the course of the reaction." Col. 3, lines 36-44.
On the other hand, the products obtained in accordance with the subject invention are copolymers of bisphenol A-isophthalate-terephthalate polyarylates or bisphenol A-isophthalate-terephthalate-carbonate polyarylates and a high molecular weight diprimary alcohol polyester polymer, such as, polyethylene arylate, and preferably, polyethylene terephthalate, having a high molecular weight as determined by measuring their intrinsic viscosity.
In the subject invention, polyarylate-polyethylene terephthalate polymers, are transparent, and tough. They have higher use temperatures than polyethylene terephthalate and are capable of maintaining dimensional stability over a wide range of temperature, namely, covering the range from 75.degree.-175.degree. C. They are completely soluble in chlorinated solvents such as chloroform and have a single glass transition point or temperature. They are useful as molding compounds, for manufacturing films, food containers and as glazing, and production of extruded shapes.